VANCOUVER Sample - Point Of Care Patient Testing POCT

Comparative Performance Discussion of POCT and Central Laboratory Testing

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Abstract

POCT (Point-of-care testing) is a pathology testing usually performed on-site that is adjacent to

the patient and which has a quick turnaround time in terms of results generation. The reduced

sensitivity experienced at times, difficulty in interpretation, and the inconsistency in performance

make POCT not as reliable as laboratory testing. Some of the performance issues attached to

POCT and its fitness for intended purpose are the analytical quality maintenance and the

robustness of the device when used by varying users, especially the unskilled patient. Directly

comparing POCT and central laboratory results is hence difficult due to differing control-

environments of analysis, varying personnel specialty, and analytical diagnostics. When

undertaking performance assessment or quality-control, there are complexities, since a novel

analytical system is in the creation every time the disposable portion of the POCT gadget is

changed.

Introduction

POCT (Point-of-care testing) is defined as a pathology testing, which is usually

performed on-site at the time of patient consultation (1). Some of the technological

advancements that make POCT practical include the development of whole blood sensors,

potentiometry science, substrate specific electrodes in a solution, and polarography techniques in

selective electrodes (2). Tests in which the application of this technology has been done include

those for glucose, urea and creatinine, coagulation and coronary markers, glycated hemoglobin

(HbA1c), electrolytes, blood-liquid gases, and lipids. Compared to standard tests carried out in

the laboratory, the report on the discovered results contradicts on different occurrences due to

limitations on acceptable procedure and interpretations from a myriad of research data.

Comparative performance of POCT and laboratory testing

POCT can be currently used in the management of diabetes; electrolyte accompanied by

acidic-basic disturbances or in risk stratification of patients afflicted with a coronary-syndrome

(1, 3). However, the performance of POCT (usually decentralized from a laboratory setting) has

often been considered to be less reliable as compared to the central laboratory testing involving

validated instrumental analysis. Mostly, the method accuracy, cost implication (especially on the

development) and connectivity issues are usually identified to be complex and challenging to

assess, hence acting as great impediments to full adoption of POCT. As an example, in the

evaluation of urine assays and body oral fluid assays on-site-test, outcomes were compared to

results of GC/MS analysis (4). Reliable results were achieved for urine on-site devices with

accuracies of up-to 99% for the benzodiazepine test, but ease of performance differences and

results interpretation were encountered, with oral fluid devices. The low sensitivity, difficulty in

interpretation, and the inconsistency in performance make POCT not as reliable as laboratory

testing.

Some of the performance issues attached to the POCT novel-technology and its fitness

for intended purpose are the analytical quality maintenance and the robustness of the device

when used by varying users especially the untrained patient (5). In a study involving diabetic

patients using different POCT instruments, 19 to 58% of patients' measurements deviated from

the conventional value hence unacceptable from ISO standard quality target that 95% of

measurements by diabetics be within ±20% of laboratory test (6).

There are problems associated with direct comparison of POCT and central laboratory

results whereby in the latter the experimental layout is within a controlled environment while in

the former the test is decentralized to varying patient environments and the interferences are not

equal with complexity in adjustments (7). For POCT also the condition is unique since the

systems and networks maintaining automated quality control carryout a clinical performance

assessment integrating data into virtual records and real medical results while laboratory results

are directly computed from the instrument reading (8, 9).

In the research, there are always discrepancies that are reported between POCT and

central laboratory results in most studies that evaluate the efficiency of the devices in controlled

laboratory set-ups or field experimental setups involving patients. The detection sensitivity of

both systems vary due to differences in the analyte and chemical systems applied where mostly

the POCT uses immunoassay based reactivities while for central laboratories separate sample

chemical-matrixes before quantification (10, 11). The level of training of the laboratory

personnel and patient or practitioner is different and hence the instrumental handling is hence

affected with accuracy in sample injection and analyte formulation compromised for POCT in

diagnostics (12).

The personnel using most POCT devices in both experimental and clinical diagnostics are

not required to possess special laboratory analytical skills, unless there are sensitive composition

tests being done such as the anticoagulation assays (13). Short duration training is adequate to

get a caregiver or patient to be apt in technicalities of analytics like in blood-glucose

determination for diabetics using glucose-strips (8, 14). During the analysis, the sample clarity is

paramount and non-turbid samples with no impurities (for body fluids) are the most preferred to

avoid false-positives or false negatives in the immunoassays. The purity of the samples is

significant with preference for freshly collected sample-units since the sensitivity attached to

immuno-antibody or chemical reactions in POCT kits is very immense (13, 15).

Performance assessment of the POCT devices, the undertaking of quality control and

proficiency testing are fundamental practices to ensure that the technology involved is reliable

enough and produces valid results for medical interventions without risking the patient’s life

(16). The electronic configuration or control sample quality control may at times be used in the

verification of the performance characteristics accuracy (2). It is because of the incapability of

performing exact quality-control since a novel analytical system is created every time the

disposable portion of the POCT gadget is changed to serve a new patient. Precision and linearity

of the results when compared with standard tests in a central laboratory have been shown to be

affected by the personnel ability to operate the device and the repeatability of similar procedures

with precise analyte-limits. Some tests also incorporate derived variables hence reducing

accuracy of the obtained measurements (17).

With the above issues creating measurement uncertainty for POCT devices results, the

impact on result interpretation is complicated since the outcome is used to make a medical

decision in-order to either administer treatment (e.g. dialysis after glucose determination) or

recommend an alteration of medication (12, 18). The tolerance allowed for the associated

uncertainty may be surpassed by the deviation observed with subsequent use of central

laboratory results which compromise the quality of interpreted parameter outcomes and either

the results are over or under reported (19).

There is a plethora of procedures by which improved performance of POCT can be

achieved to create a desired implication on health outcomes. While augmenting the performance

or capabilities for most POCT technological devices in order to embrace novel analytical

techniques, there are paramount fundamental requirements that need integration into the systems

(1, 19). These include:

- The POCT devices have to be simple in usage and remain robust for analysis results

validity, to avoid compromised performance risking patient’s health.

- The devices have to encompass or contain all the experimental analytes needed for every

respective patient testing on a singular platform (be comprehensive enough) (4).

- Connectivity is also crucial to both the electronic patient data and online record database

having all laboratory medical results for comparative reporting and easy patient access

(20), and

- Connectivity that makes possible a linked dialogue between the respective patient and

clinical practitioner wherever the POCT device system is utilized directly by a household

patient without attendance by the clinical reviewer.

Conclusion

A paramount issue with research in regard to the utilization of POCT is the diminished

rate of the technology adoption, partly attributable to the limitations currently on evidence but

also demonstrating that POCT augments analytical outcomes. The lack of evidence of utility

compromises the transfer of the technology in what creates a paucity of positive research data.

Even with some analytes of POCT being as effective as central laboratory testing due to

improved patient and provider general satisfaction, the implications derived on technology-

development costs are debilitating. Significant impact and adoption lie in augmentation of

methodologies for novel clinical parameters, interrelated operability elucidations with integrated

cost reimbursement schemes by public authorities.

References

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Med. 2002; 22(4): 393-404.

3. Crouch DJ, Hersch RK, Cook RF, Frank JF and Walsh JM. A field evaluation of five on-

site drug-testing devices. J Analy Toxico. 2002 Oct; 26: 493-499.

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04.pdf

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phase.org/parma2011/parma_presentations/15_Timo_Kouri.pdf

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testing on linkage to HIV care: a systematic review. J Intern AIDS Soc. 2014 Jan; 17: 1-

17. Commonwealth of Australia. The use of INR point-of-care testing in general practice

[Internet]. c2005 [updated 2005 May; cited 2014 Aug 1]. Available from

http://www.otago.ac.nz/christchurch/otago013998.pdf

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pt2013.pdf

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guidance-poct.pdf

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